Query optimization: use indexes; avoid SELECT *; push filters early; use JOINs not subqueries; analyze execution plans; partition pruning; materialized views; statistics; limit result sets; avoid functions on indexed columns (e.g., WHERE YEAR(date)=2024 prevents index use—use...
This hard-level SQL question appears frequently in data engineering interviews at companies like PayPal. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (join, optimization, partition) will help you answer variations of this question confidently.
This is a senior-level question that tests architectural thinking. Lead with the high-level design, then drill into specifics. Discuss trade-offs explicitly - there is rarely one correct answer. Show awareness of scale, fault tolerance, and operational complexity.
Query optimization: use indexes; avoid SELECT *; push filters early; use JOINs not subqueries; analyze execution plans; partition pruning; materialized views; statistics; limit result sets; avoid functions on indexed columns (e.g., WHERE YEAR(date)=2024 prevents index use—use range instead). Why it matters: Design choices compound at scale—wrong approach can cause 100× overhead. Scalability trade-offs: Profile before optimizing; validate on sample then full. Cost implications: Suboptimal choices multiply at billion-row scale.
This answer is partially locked
Unlock the full expert answer with code examples and trade-offs
Practice real interviews with AI feedback, track progress, and get interview-ready faster.
Pro starts at $24/mo - cancel anytime
Get the most asked SQL questions with expert answers. Instant download.
No spam. Unsubscribe anytime.
Paste your answer and get instant AI feedback with a FAANG-level improved version.
Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.